Thermoplastic resins can exhibit excellent physical properties such as low specific gravity, good moldability and good impact resistance, as compared with glass or metal. Recently, with the trend of low cost, larger and light electronics, plastic products made of thermoplastic resins are quickly replacing existing glass or metal-based products, thereby broadening applications thereof from electronics to automobile components. In line with this trend, functions as exterior materials and external appearance become increasingly important, and development of resins having good scratch resistance for ensuring stability from exterior shock or scratch, or flame retardancy for ensuring stability against fire is highly demanded.
Acrylic resins, specifically poly(methyl methacrylate) resins, have excellent transparency, weather resistance, mechanical strength, surface gloss, adhesion, and the like, particularly remarkably excellent scratch resistance. However, acrylic resins have poor impact resistance and flame retardancy.
In order to overcome these problems while achieving mechanical properties including scratch resistance, one method is to mix a polycarbonate (PC) and an acrylic resin, for example poly(methyl methacrylate) (PMMA), to prepare PC/PMMA resins. In order to prepare PC/PMMA resins having high compatibility, acrylic copolymers having a high index of refraction are used, thereby developing an alloy resin of polycarbonate and acrylic resins having high scratch resistance. However, the alloy resin exhibits low flame retardancy due to a low content of a flame retardant and is likely to suffer from deterioration in mechanical properties including heat resistance when containing a flame retardant. Furthermore, when preparing a resin by adding phosphorus monomer-based flame retardant, the flame retardant can easily migrate from the resin, thereby causing environmental contamination.
In order to overcome these problems, there is an increasing need for polycarbonate resin compositions including a copolymerizable phosphorus-based acrylic monomer.